You are right to be concerned about your son's behavior. Early intervention on a problem is very important for children to develop normally. So much is going on, socially, cognitively, physically. I agree with you that seeing a child psychologist is a good idea. A comprehensive evaluation would be helpful to you, your son and everyone who works with him. An evaluation will be able to give you more insight into what is going on with your son and appropriate treatment interventions. Be aware that diagnosis is tricky with children, because of developmental factors. So realize that whatever he may be diagnosed with now, if he is given a mental health diagnosis, will likely change over the years. It is the nature of children, which is why periodic assessments are important for proper care. Ask your doctor, his teacher or school social worker for names of child psychologists near you.
In my experience, yes children can be taught skills to manage their behavior, whether it be anger, anxiety or impulsive behaviors. They need the help and support of their parents to be successful. At his age I would not think hormones would be a factor, but certainly the possibility of any physical factors should be ruled out. If he hasn't had a physical or well child visit with his doctor recently it would be a good idea to do that. Diet does influence how we feel and act, the question is how much. It is very individual with some people being more sensitive than others. I would encourage you to just focus on a healthy, well balanced diet. If you have strong suspicions of food sensitivities the best thing to do is keep a detailed food diary which documents what he eats, when and behavior. Good luck to you, your son and your family!